Which condition causes fatal compression of the fourth ventricle, leading to obstructive hydrocephalus and depressed respiratory drive with coma?

• A. Cerebellar hemorrhage
• B. Subarachnoid hemorrhage
• C. Locked-in syndrome
• D. Persistent vegetative state

Answer: (A)

A large cerebellar hemorrhage in the posterior fossa can rapidly expand and press on the fourth ventricle, producing fatal compression of this CSF outflow route. When the fourth ventricle is compressed, CSF can no longer exit into the subarachnoid space, leading to obstructive (noncommunicating) hydrocephalus. The resulting rise in intracranial pressure affects the brainstem, including the medullary respiratory centers, which can depress respiratory drive and lead to coma. This combination—posterior fossa expansion, fourth ventricle compression, obstructive hydrocephalus, and brainstem dysfunction—fits cerebellar hemorrhage best.

Subarachnoid hemorrhage can cause hydrocephalus, but it’s usually from impaired CSF absorption or diffuse subarachnoid blood rather than direct fourth ventricle compression. Locked-in syndrome arises from a ventral pontine lesion with preservation of consciousness, not from fourth ventricle compression. Persistent vegetative state reflects severe cortical/subcortical injury rather than an acute brainstem compression syndrome.